Method for the expulsion of a plant protection composition and spray gun

ABSTRACT

The invention relates to a method for ejecting a pesticide by means of a fluid chamber  3 , which communicates via an electrically controlled fluid valve  48  having a spout  22 . The method comprises the following steps: determining a pressure and a duration of a time interval for ejecting the pesticide, filling the pesticide into the fluid chamber  3 , applying a defined pressure on the pesticide in the fluid chamber  3  and opening the fluid valve  48  by means of an electric control signal for a specific, previously determined time interval and closing the fluid valve  48  after the time interval has expired, so that a defined volume or a defined weight of the pesticide is ejected by the spout  22 . The invention further relates to a spray gun for carrying out the method and to the use of said spray gun for ejecting liquid, in particular gel-like, pesticide.

The present invention relates to a method for the expulsion of a plantprotection composition. In the method, the plant protection compositionis filled into a fluid chamber. Subsequently, a pressure is exerted onthe plant protection composition located in the fluid chamber and theplant protection composition is expelled via a spray orifice.Furthermore, the invention relates to a spray gun for the expulsion of afluid, in particular a plant protection composition. The spray guncomprises a fluid chamber and a spray orifice which communicates withthe fluid chamber. Furthermore, the spray gun has a pressure devicewhich is coupled to the fluid chamber and by means of which a pressurecan be exerted on the fluid located in the fluid chamber.

It is known to expel liquids by means of what is known as a spraybottle. In this case, a pumping mechanism acts directly on the liquidwhich is expelled through a nozzle. Furthermore, in spray devices, it isknown to use a pumping mechanism to increase the air pressure in achamber which accommodates the water to be expelled. When a trigger isthen actuated, the water located in the chamber is sprayed outwardthrough a nozzle on account of the compressed air in the chamber.

EP 0 462 749 B1 discloses a spray gun which is actuated by means of ahand lever. The spray gun has a connection for a liquid supply, viawhich connection pressurized liquids are supplied to the spray gun. Atthe outlet end of the spray gun, an outlet nozzle is provided forexpelling liquid in a particular spray pattern. Provided between theconnection for the liquid supply and the outlet nozzle is a controlvalve which can be opened by means of a trigger.

EP 1 136 135 B1 describes a fluid pump dispenser having a pistonmechanism. In this pump dispenser, the formation of droplets or drops ofthe product at the outlet orifice is avoided in that the product isdrawn into the pump chamber at the start of each piston return stroke.

DE 196 12 524 A1 describes a spray gun which is designed particularlyfor the expulsion of medium- to high-viscosity liquids, such as, forexample, pasty adhesives. The substance to be applied is spread inparticular over the surface of a sheet-like structure. The spray gun hasa substance supply connection piece and a substance outflow connectionpiece. Arranged between these is a piston chamber in which a piston canbe moved back and forth. The piston is coupled to a switching lever. Bythe switching lever being actuated, the throughflow through the pistonchamber can be closed and opened as a result of the movement of thepiston. Provided at the switching lever is a sensor switch which is inthe form of an inductive proximity switch and switches off substancetransport when the switching lever approaches in a stipulated proximitystate. In this case, the propulsive pressure of substance transport isreduced before the closure of substance transport takes place. This isintended to prevent material from continuing to flow.

Furthermore, spray guns in which a liquid is atomized into small dropswith the aid of a pressure difference are known. For example, thesubstance to be expelled can be sucked out of a container with the aidof a Venturi tube and then atomized. Spray guns of this type are used,for example, for the spraying of paint. In this case, it is also knownto put the paint under pressure by means of a pump and to press itthrough a nozzle such that the paint is finely atomized.

Finally, U.S. Pat. No. 5,441,180 discloses a spray gun which is designedin particular for the expulsion of plant protection compositions. Thisspray gun comprises a reservoir for the plant protection composition tobe expelled. Furthermore, the spray gun comprises a pivotable trigger bymeans of which a piston can be moved. As a result of the movement of thepiston, the volume in a chamber in which the plant protectioncomposition to be expelled is located is reduced, so that the plantprotection composition is expelled. When the trigger is pivoted backagain, the piston is moved in the opposite direction, so that the volumeof the chamber increases. This generates a negative pressure which sucksthe plant protection composition back out of the expulsion orifice.

Plant protection compositions are usually applied in the form of liquidactive substance preparations. These are prepared, as a rule, by thedilution of commercially customary active substance concentrates, suchas, for example, suspension concentrates (SC), oil dispersions (OD),capsule dispersions (CS), emulsifiable concentrates (EC), dispersibleconcentrates (DC), emulsions (EW, EO), suspoemulsion concentrates (SE),solution concentrates (SL), water-dispersible and water-soluble powders(WP and SP), and water-soluble and water-dispersible granules (WG, SG)with or in water. In addition, use is also made of products in the formof active substance solutions, which contain the active substance in aconcentration suitable for application, what are known as ULVs.Furthermore, in order to combat arthropodic pests, use is frequentlymade of active substance-containing gels, which, before being applied,are optionally diluted with water to the desired applicationconcentration. Therefore, here and in the following text, the term“plant protection composition” is used both for liquid active substanceformulations, including active substance-containing gel formulations,having an active substance concentration suitable for application, andfor liquid active substance preparations, including diluted gelformulations, which are obtainable by the dilution of active substanceconcentrates.

When plant protection compositions are expelled or sprayed by means of aspray gun, it is particularly important that the spray gun can behandled safely and easily. The spray gun should be suitable for mobileuse, that is to say it should be capable of being carried easily by aperson. Furthermore, it is particularly important that the expelledfluid, that is to say the plant protection composition, can be meteredvery accurately. Finally, the plant protection composition should becapable of being applied precisely to a desired area from a specificdistance by means of the spray gun. In this case, it should be ensuredthat, during the expulsion operation, no plant protection compositioncan pass into regions which are not intended to come into contact withthe plant protection composition. In particular, it should be ensuredthat there is no possibility of the user coming into contact with theplant protection composition. Moreover, dripping at the end of theexpulsion operation should be avoided. The spray gun should, inparticular, also be suitable for the application of activesubstance-containing gels, for example active substance-containing gelsfor combating arthropodic pests, and should allow targeted application,for example in the form of spots or strips/strands. Moreover, the spraygun should be insensitive to inhomogeneities of the liquid plantprotection composition, such as may occur, for example, during thepreparation of the active substance preparation used for application,when the commercially available active substance concentrates arediluted with or in water to the concentration desired for application.

It is the object of the present invention to provide a method and aspray gun of the type initially mentioned, with which it is possible toachieve very accurate metering of the expelled fluid. Furthermore, anoutflow of the fluid after the conclusion of the expulsion operation,that is to say a dripping of fluid, is to be prevented.

According to the invention, this object is achieved by a method havingthe features of claim 1 and a spray gun having the features of claim 9.Advantageous refinements and developments can be gathered from thedependent claims.

In the method according to the invention, the plant protectioncomposition is expelled by means of a fluid chamber which communicateswith the spray orifice via an electrically activatable fluid valve. Inthe method, a pressure and a length of a time interval for the expulsionof the plant protection composition are set. Subsequently, the plantprotection composition is filled into the fluid chamber. The previouslyset pressure is exerted on the plant protection composition located inthe fluid chamber. Finally, the fluid valve is opened for the previouslyset time interval by means of an electric control signal and is closedafter the end of the time interval so that a defined volume or a definedweight of the plant protection composition is expelled through the sprayorifice. By way of the electric activation of the fluid valve, it ispossible to control the expulsion time very precisely. As a result, thequantity of the plant protection composition which is expelled during anexpulsion operation can be metered very accurately.

In the method according to the invention, in particular the pressureexerted on the plant protection composition located in the fluid chamberis kept constant during the time interval in which the fluid valve isopen. Since the quantity of plant protection composition that isexpelled is not only dependent on the length of time that the fluidvalve is open but is also dependent on the pressure which is exerted onthe plant protection composition, the quantity expelled can be setaccurately in a simple manner. Specifically, it is not necessary to takeinto consideration a variable pressure profile during the expulsionoperation.

According to one refinement of the method according to the invention,the pressure exerted on the plant protection composition located in thefluid chamber is generated by means of a pressurized gas or a pump. Thepressurized gas can be provided for example from a gas cylinder whichcontains a large quantity of highly pressurized gas, e.g. air.Furthermore, the pressurized gas can be generated by a compressor. As aresult, a constant pressure for the expulsion operation can be providedin a simple and cost-effective manner.

According to one refinement of the method according to the invention,the distance between the fluid valve and the spray orifice is less than50 cm, in particular less than 10 cm and advantageously less than 2 cm.Furthermore, according to one refinement of the method according to theinvention, the fluid volume located between the spray orifice and thefluid valve is less than 14 cm³, preferably less than 2.8 cm³, furtherpreferably less than 1.4 cm³ and in particular less than 0.57 cm³.Particularly preferably, the fluid valve is arranged directly at thespray orifice.

In the method according to the invention, in particular a plantprotection composition in the form of a fluid (liquid) is expelled andconsequently applied. Fluids suitable for application have as a rule adynamic viscosity in the range of from 0.5 to 1000 mPa·s, frequentlyfrom 0.8 to 500 mPa·s (determined by Brookfield's rotational viscometryto DIN 53019 (ISO 3219) at 25° C. and with a shear gradient of 100 s⁻¹).Suitable fluids may be Newtonian liquids or non-Newtonian liquid, thelatter preferably being shear-thinning, that is to say viscoelastic orpseudoplastic non-Newtonian fluids.

According to one embodiment of the method according to the invention,low-viscosity fluids are expelled, that is to say in particular liquidshaving a viscosity of no more than 50 mPa·s, in particular no more than30 mPa·s, e.g. from 0.5 to 50 mPa·s, in particular from 0.8 to 20 mPa·s(determined by Brookfield's rotational viscometry to DIN 53019 (ISO3219) at 25° C. and with a shear gradient of 100 s⁻¹). These includeboth organic liquids, in particular solutions of plant protection activesubstances, in organic solvents, and also aqueous liquids, for exampleaqueous active substance solutions, but also emulsions, suspoemulsionsand suspensions, in which the plant protection active substance ispresent in dispersed form in a coherent aqueous phase.

According to a further refinement of the method according to theinvention, the plant protection composition expelled is a gel-likefluid. Unlike low-viscosity fluids, gel-like fluids have an increasedviscosity. As a rule, such gel-like fluids are viscoelastic and as arule have at 25° C. a zero shear viscosity η0 of at least 100 mPa·s andin particular at least 200 mPa·s. However, the dynamic viscosity of thegel-like fluid will not as a rule exceed a value of 1000 mPa·s, inparticular 500 mPa·s and especially 300 mPa·s (determined byBrookfield's rotational viscometry to DIN 53019 (ISO 3219) at 25° C. andwith a shear gradient of 100 s⁻¹) and lies in particular in the range offrom 30 to 1000 mPa·s, frequently in the range of from 30 to 800 mPa·sand in particular in the range of from 50 to 500 mPa·s. Preferably, at25° C. the limit value of the viscosity in the case of an infinite sheargradient η_(∞) is no more than 300 mPa·s and in particular no more than250 mPa·s. The gel-like liquid may be a gel formulation which containsthe active substance in the concentration required for application. Inparticular, it is a liquid which is obtained by dilution of a gelformulation to the concentration required for application.

The rheological properties of the fluid or the formulation of the fluidare selected in particular such that they are temperature independent orat least scarcely temperature dependent. Preferably, the rheologicalproperties of the fluid or the formulation of the fluid change within atemperature range of from 15° C. to 35° C. only such that the quantityexpelled per unit time at a given pressure at a particular nozzle orspray orifice fluctuates only in a range of +/−10%, in particular in arange of +/−5%.

According to a development of the method according to the invention, thelength of the time interval is set by a previously carried outcalibration. In the calibration, the dependence of the expelled volumeor weight of a plant protection composition of a particular viscosity onthe exerted pressure and the length of the time interval is determined.In this way, the parameters for the expulsion operation are set veryprecisely beforehand for a particular plant protection composition.Before the fluid valve is opened, a defined pressure, which was setduring the previously carried out calibration, is generated. If a plantprotection composition of known viscosity is now filled into the fluidchamber, it is possible to determine very accurately from the previouslycarried out calibration the length of the time interval in order toexpel a desired volume or weight of the plant protection composition.For this previously defined time interval, in the case of the methodaccording to the invention, the fluid valve is opened and the plantprotection composition is expelled through the spray orifice. Thisachieves very accurate metering of the expelled volume or weight of theplant protection composition.

The spray gun according to the invention is distinguished in that anelectrically activatable fluid valve for opening and closing the passagefrom the fluid chamber to the spray orifice is arranged at the sprayorifice. The fluid valve is data-coupled to an electric control deviceby way of which an electric control signal for opening the fluid valvefor a particular previously defined time interval and for closing thefluid valve after the end of the time interval can be generated so thata defined volume or a defined weight of the fluid is expelled via thespray orifice.

The spray gun according to the invention is suitable in particular forcarrying out the method according to the invention. Therefore, it alsohas the same advantages. By means of the spray gun according to theinvention, in particular the expelled volume of fluid or the expelledweight of fluid can be set very precisely.

A spray gun is understood within the meaning of the invention to be anappliance by means of which a fluid can be expelled, squirted, sprayedor atomized through an orifice. However, upon outflow, a fluid jet, inparticular, can be generated by the spray gun according to theinvention.

According to one refinement of the spray gun according to the invention,the control device comprises a memory for storing a previously setpressure and a previously set length of the time interval. During thespraying operation, the control device then controls the fluid valve andthe pressure device such that the previously stored pressure is exertedon the fluid during the spraying operation and the fluid valve is openedprecisely for the stored length of the time interval.

According to another refinement of the spray gun according to theinvention, the previously set pressure is not stored. Instead, anadjustable pressure valve is provided and is permanently set in orderthat it ensures that a particular pressure is always exerted on theplant protection composition in the fluid chamber.

According to one refinement of the spray gun according to the invention,the pressure device comprises a pump, by means of which the pressure canbe exerted on the fluid located in the fluid chamber. This refinementhas the advantage that it allows a very simple structure of the spraygun.

According to another refinement of the spray gun according to theinvention, the pressure device comprises at least one cylinder in whicha piston for exerting the pressure on the fluid located in the fluidchamber is mounted movably. In this way, a fluid located in the fluidchamber is pressed out of the cylinder by the movement of the piston inthe latter. In such piston metering or piston pumping devices, theproblem often arises that at the end of an expulsion operation, at whichthere is scarcely any more fluid in the fluid chamber, the pressure bywhich the fluid is expelled drops. The result of this pressure drop isthat the expelled fluid jet stalls. The quantity of fluid last expelledno longer has the same expulsion velocity as fluid volumes previouslyexpelled, and therefore the fluid expelled at the end no longer arrivesat the target in the same way as the previous fluid volumes. As a resultof this, part of the expelled fluid jet falls onto a region between thetarget area and the spray gun. This is particularly disadvantageous whenthe spray gun is used for the expulsion of plant protectioncompositions.

In the spray gun according to the invention, this drop in velocity atthe end of fluid expulsion can be prevented, for example, in that at thecylinder there is provided a sensor by way of which a defined positionof the piston, in which there is still sufficient fluid in the fluidchamber during the expulsion operation, can be detected. The sensorensures that the expulsion operations with a filling of the fluidchamber can be carried out such that even during the last expulsionoperation the maximum pressure is still exerted by the piston on theremaining fluid in the fluid chamber. Even the quantity of fluidexpelled last therefore still has the same expulsion velocity as thefluid volumes previously expelled. In this way, a coherent fluid jet, inwhich the entire expelled fluid has substantially the same velocity, canbe generated and so the entire quantity of fluid expelled during thelast expulsion operation reaches the desired target area. In particular,no drop in expulsion velocity occurs at the end of this expulsionoperation, thereby ensuring that no regions between the target of theexpulsion operation and the spray orifice of the spray gun come intocontact with the expelled fluid. This is advantageous particularly whenthe expelled fluid is a plant protection composition, in particular aliquid, in particular gel-like, high-viscosity plant protectioncomposition.

The defined position of the piston is selected, in particular, such thatthere is still sufficient fluid in the fluid chamber to ensure that apressure drop will not occur at the spray orifice at the end of the lastexpulsion operation. In particular, in this position, the piston has notyet reached its end position in the cylinder in which it butts against acylinder wall.

In one refinement of the spray gun according to the invention, thedefined position of the piston is detected by the sensor by means of amagnetic field generated or varied by the piston. For example, apermanent magnet may be integrated into the piston, said permanentmagnet generating a magnetic field, the field strength of which at thelocation of the sensor depends on the position of the piston. If thefield strength of the magnetic field at the sensor exceeds or fallsbelow a specific limit value, the state of the sensor changes. In thiscase, the limit value for the field strength of the magnetic field isset such that the piston is in this case in the desired position withinthe cylinder at which there will be no pressure drop during the lastexpulsion operation.

The sensor comprises, in particular, what is known as a reed contact. Ina reed contact, an electrical contact is closed when the field strengthof the magnetic field at the location of the sensor exceeds a limitvalue.

Thus, during the expulsion operation, the sensor of this refinement ofthe spray gun according to the invention detects the position of thepiston by means of a measured value which depends directly on theposition of the piston in the cylinder. As a result, the position of thepiston in the cylinder can be detected with great accuracy. By way ofsubsequent electronic processing of the signal generated by the sensor,the last expulsion operation can be detected very precisely, with theresult that a pressure drop at the end of the last expulsion operationis avoided.

According to a development of the spray gun according to the invention,the pressure device furthermore comprises a compressed gas line which iscoupled to the fluid chamber for exerting the pressure on the fluidlocated in the fluid chamber. The compressed gas, which is supplied viathe compressed gas line, can exert a pressure on the fluid directly.Furthermore, it is possible for the compressed gas to exert a pressurevia the movable piston on the fluid which is located in the fluidchamber. To this end, for example in the cylinder there may be formed apressure chamber at which there is formed a cylinder orifice which isconnected to a first connection for a compressed gas line, in particulara compressed air line. Thus, compressed gas can pass into the pressurechamber via the cylinder orifice. When the pressure in the pressurechamber exceeds the pressure in the fluid chamber, the movable piston ispressed in the direction of the fluid chamber in which the fluid islocated. Thus, the volume of the pressure chamber is increased and thevolume of the fluid chamber reduced, as a result of which the fluid ispressed out through the first cylinder orifice when the fluid valve isopened. At the same time, by the first connection being connected to thecompressed gas line, the pressure can be kept constant in the pressurechamber, so that a constant pressure is exerted on the fluid in thefluid chamber by the piston during the expulsion operation.

According to a further refinement of the spray gun according to theinvention, said spray gun additionally or alternatively has acompression spring which acts between a stop and the piston. Thecompression spring can exert on the piston a force in the direction of areduction in the volume of the fluid chamber. In this case, it ispossible to configure the spray gun such that no pressure chamber isformed and the cylinder is not connected to a compressed gas line. Inthis case, the piston pressure is generated solely by the compressionspring. The pressure exerted on the fluid during the filling of thefluid chamber must then optionally exceed the pressure exerted by thecompression spring, so that, during the filling of the fluid chamberwith the fluid, the compression spring is compressed and the volume ofthe fluid chamber increases. Moreover, it is possible, however, toprovide the compression spring in addition to the pressure chamber. Inthis case, the compression spring supports the pressure which is exertedon the piston by the compressed gas in the pressure chamber.

Furthermore, the spray gun according to the invention may have aregulating device, by means of which the movement of the piston in thecylinder and therefore the maximum volume of the fluid chamber can belimited. Thus, the fluid volume expelled during the expulsion operationscan be set by means of the regulating device.

According to another refinement, the sensor is adjustable in thelongitudinal direction of the cylinder. In this case, the expelled fluidvolume of a series of fluid expulsions can be set by the position of thesensor being set in relation to the cylinder.

According to a development of the spray gun according to the invention,the latter has a second connection for a fluid reservoir. The fluidreservoir may be integrated into the spray gun. If, however, the fluidreservoir is intended to accommodate relatively large quantities offluid, the fluid reservoir is provided separately from the spray gun,and so the fluid is supplied to the spray gun via the second connection.This second connection may be connected to a further cylinder orifice,via which fluid can be supplied to the fluid chamber. However, it isalso possible for the second connection to be connected to the cylinderorifice via which the fluid is pressed to the spray orifice, and so thefluid can be conveyed into the fluid chamber via the second connectionand the cylinder orifice. Thus, the fluid then flows through thecylinder orifice both into the fluid chamber of the cylinder and out ofthis fluid chamber.

In this case, it is possible, furthermore, to design the fluid valve asa first 3/2-way valve, in which, in a first position, a fluid passagefrom the cylinder orifice to the spray orifice is provided, and, in asecond position, a fluid passage from the second connection to thecylinder orifice is provided.

A 3/2-way valve is understood to be a valve with three connections andtwo switch positions. The fluid reservoir or the second connection, thespray orifice and the cylinder orifice are connected to the threeconnections of the valve. In the first position of the valve, a passagefrom the cylinder orifice to the spray orifice is provided, the passagefrom the fluid reservoir or the second connection to the cylinderorifice being closed. In the second position of the valve, a fluidpassage from the fluid reservoir or the second connection to thecylinder orifice is provided, the passage from the cylinder orifice tothe spray orifice being closed. Thus, by means of the first 3/2-wayvalve, both fluid transport to the spray orifice during the expulsionoperation and fluid transport for filling the fluid chamber of thecylinder for the fluid are carried out.

Furthermore, in the spray gun according to the invention, a compressedgas valve configured as a second 3/2-way valve may be arranged betweenthe first connection, via which a compressed gas can be supplied to thespray gun, and the cylinder orifice for introducing the compressed gas.In the first position of this compressed gas valve, a compressed gaspassage from the first connection to this cylinder orifice is provided.In the second position of the compressed gas valve, a reduction in thepressure of the compressed gas within the pressure chamber is madepossible. For example, in the second position, a compressed gas passagefrom the cylinder orifice into the open may be provided.

According to a development of the spray gun according to the invention,the fluid reservoir is connected to a device for the provision ofcompressed gas, in particular compressed air. The device may be, forexample, a compressed air tank, a compressor and a hand pump. However,the fluid may also be put under pressure directly, for example by apump. In addition, the fluid reservoir is connected via a line to thefirst connection of the compressed gas valve. A connection from thecompressed gas valve to the fluid reservoir is thus provided. Thisconnection may be integrated into the spray gun or be formed separatelyfrom the spray gun. In the second position of the compressed gas valve,the pressure chamber can thus be acted on with compressed gas.Furthermore, the fluid reservoir is acted on with compressed gas inorder to effect fluid transport for filling the fluid chamber of thecylinder.

According to a development of the spray gun according to the invention,the sensor is coupled to the first and the second 3/2-way valve. In thiscase, the sensor switches the first and the second 3/2-way valve intothe second position when the piston has reached or passed the definedposition, so that fluid is conveyed by means of the compressed gas fromthe fluid reservoir into the fluid chamber via the first 3/2-way valve.After the last expulsion operation has been ended, the fluid chamber ofthe cylinder is thus refilled with fluid automatically via the two3/2-way valves. Switching of the valves takes place in particularelectronically. Preferably, the two valves are changed oversimultaneously, or first of all the first 3/2-way valve for the fluid ischanged over and shortly thereafter the second 3/2-way valve for thecompressed gas.

According to a further refinement of the spray gun according to theinvention, the fluid chamber and the spray orifice are connectedtogether via a connecting line. In this case, the fluid valve isarranged adjacent to the spray orifice in the connecting line and inparticular is arranged directly at the spray orifice. The distance ofthe spray orifice from the fluid valve is less than 50 cm, preferablyless than 10 cm, further preferably less than 5 cm and in particularless than 2 cm. In this case, the fluid volume located between the sprayorifice and the fluid valve is less than 14 cm³, preferably less than2.8 cm³, further preferably less than 1.4 cm³ and in particular lessthan 0.57 cm³. The fluid valve is thus positioned as close as possibleto the spray orifice. As a result, it is possible to prevent drippingeven when viscous or highly viscous fluids are expelled by means of thespray gun. Specifically, it has been found that in this case drippingcannot be prevented by for example a ball valve which is arranged at thespray orifice. However, such dripping can be prevented by theelectronically activated fluid valve directly at the spray orifice.

The spray gun according to the invention also has in particular atrigger, for example a manual trigger. An expulsion operation isinitiated by this trigger once the fluid chamber has been filled.However, before the control device opens the fluid valve for expellingthe fluid following the actuation of the trigger, a check isadvantageously carried out as to whether the pressure exerted on thefluid in the fluid chamber corresponds to a pressure which was setduring a previously carried out calibration. This pressure is stored inthe memory of the control device for each fluid that can be used withthe spray gun. The current pressure within the fluid chamber or withinthe pressure chamber, via which the pressure is exerted on the fluid inthe fluid chamber, is detected by means of a pressure sensor which isdata-coupled to the control device. Only when the measured pressure liesideally at the previously stored pressure or in a previously storedpressure range is the fluid valve opened for the previously defined timeinterval following the actuation of the trigger. The time intervalassociated with the respective pressure is also stored in the memory ofthe control device for a fluid of a particular viscosity.

The electrically activatable fluid valve of the spray gun according tothe invention is a valve which can receive an electronic control signalwhich effects the opening and closing of the valve. In order to open andclose the valve, the valve can be actuated for exampleelectromagnetically. For example, a particular voltage can be applied tothe valve in order to open the valve. This voltage leads to anelectromagnetic actuation of the valve, in which the valve is moved intoan open state. If the voltage is no longer applied, the valve isautomatically closed. Thus, in order to open the fluid valve for thedefined time interval, the control device applies a voltage to the fluidvalve for this time interval, said voltage keeping the fluid valve in anopen state.

The trigger, too, is in particular an electronic trigger, on theactuation of which a control signal is transmitted to the controldevice. Finally, the further fluid valves for filling the fluid chamberand the compressed gas valve can also be electrically activated andelectromagnetically actuated. On account of the electronic control ofthe valves and the electronic trigger for the spray gun, it is possibleto design the mechanical structure of the spray gun very simply. Areduction in the weight of the spray gun can thereby be achieved, thisbeing advantageous particularly in the case of mobile use of the spraygun. What is achieved by the electronic control of the valves is thatthe fluid expulsion can be controlled very accurately, this beingimportant particularly when plant protection compositions are beingexpelled.

In an alternative refinement of the spray gun according to theinvention, a first and a second fluid chamber are formed in thecylinder. In the first fluid chamber, at least one first cylinderorifice is formed. In the second fluid chamber, at least one secondcylinder orifice is formed. In this alternative refinement, the fluidaccommodated in the first fluid chamber can be pressed out by fluidbeing pressed under pressure into the second fluid chamber, as a resultof which a force is exerted on the piston in the direction of areduction in the size of the first fluid chamber. Conversely, the fluidaccommodated in the second fluid chamber can be pressed out by fluidbeing pressed under pressure into the first fluid chamber, as a resultof which a force is exerted on the piston in the direction of areduction in the size of the second fluid chamber. In this refinement ofthe spray gun according to the invention, the pressure chamber which canbe filled with compressed gas has thus been replaced by a fluid chamber.In this case, pressure is exerted on the piston not by a compressed gas,but by the fluid located in the other fluid chamber in each case, sothat the fluid is expelled alternately out of the two fluid chambers.The advantage of this refinement is that the intermissions between twoseries of expulsion operations of the spray gun are very much shorter,since it is no longer necessary to wait until the fluid chamber hasfilled again in order to start the next series of fluid expulsions.Specifically, the filling of one fluid chamber causes the expulsion offluid via the other fluid chamber.

According to a development of this refinement of the spray gun accordingto the invention, a first sensor is provided in the first fluid chamberand a second sensor is provided in the second fluid chamber. Asexplained above, a defined position of the piston, in which fluid isstill located in the respective fluid chamber during the expulsionoperation, can be detected by the sensor. The respective fluid valve isclosed by means of the sensor when the defined position of the pistonhas been detected.

According to a development of this refinement of the spray gun accordingto the invention, the sensors can be adjusted in the longitudinaldirection of the cylinder. In this case, the expelled fluid volume of aseries of fluid expulsions can be set by the position of the sensorsbeing set in relation to the cylinder.

According to a further alternative refinement of the spray gun accordingto the invention, said spray gun comprises a first and a secondcylinder. A first fluid chamber with a first cylinder orifice is formedin the first cylinder, and a second fluid chamber with a second cylinderorifice is formed in the second cylinder. Furthermore, a first pressurechamber is formed in the first cylinder and a second pressure chamber isformed in the second cylinder, the first and the second pressure chambercommunicating with one another and comprising a non-compressible workingfluid. The first fluid chamber is separated from the first pressurechamber by a first piston. The second fluid chamber is separated fromthe second pressure chamber by a second piston, the volume of the firstfluid chamber decreasing when the volume of the second fluid chamberincreases. Conversely, the volume of the first fluid chamber increaseswhen the volume of the second fluid chamber decreases. According to thisrefinement, the fluid accommodated in the first fluid chamber can bepressed out by fluid being pressed under pressure into the second fluidchamber, a force being exerted on the second piston and beingtransmitted to the first piston via the working fluid. Conversely, thefluid accommodated in the second fluid chamber can be pressed out byfluid being pressed under pressure into the first fluid chamber, as aresult of which a force is exerted on the first piston and istransmitted to the second piston via the working fluid.

In this refinement, the fluid valve is coupled to the first cylinderorifice and the second cylinder orifice, it being possible to produce afluid passage to the spray orifice only in each case to one cylinderorifice. Furthermore, the fluid valve can preferably also be shut offcompletely.

In this further refinement, too, the time interval between two series ofexpulsion operations can be shortened, since the filling of one fluidchamber causes the expulsion operations of the fluid out of the otherfluid chamber.

The spray orifice may be designed such that the fluid is atomized, butpreferably a liquid jet is generated. To this end, the spray orifice ispreferably surrounded by a spray nozzle which generates a liquid jetwhen the liquid or aqueous solution passes through, that is to say theliquid or solution is in particular not atomized.

The spray nozzle of the spray gun according to the invention is inparticular designed such that a plant protection composition can beexpelled by way of the spray gun, said plant protection compositionhaving been described above with regard to the method according to theinvention. The spray gun is designed in particular for a liquid plantprotection composition, the spray orifice in this case being surroundedby a spray nozzle which generates a liquid jet when the liquid plantprotection composition passes through. Furthermore, the spray gun can bedesigned for a gel-like plant protection composition. In this case thespray nozzle generates a jet when the gel-like plant protectioncomposition passes through. The gel-like plant protection compositioncan thus be applied in a punctiform manner, that is to say in the formof drops, or in a linear manner, that is to say in the form of strandsor strips. Examples of suitable spray nozzles are conical nozzleswithout a baffle plate, jet nozzles or hole-type nozzles.

Examples of gel formulations which can be applied in optionally dilutedform by means of the method according to the invention or the spray gunaccording to the invention are in particular those gel formulationswhich are used for combating arthropodic pests.

Gel formulations of this type are known, for example, from WO2008/031870. As a rule, these gels typically comprise at least oneactive substance which is active against arthropodic pests, such asinsects or arachnids (Arachnida). In addition, these gels typicallycomprise water, at least one thickener or gel former and optionally oneor more attractants and/or feeding stimulants.

The above-described spray guns are suitable in particular for theapplication of liquids which comprise one or more plant protectionactive substances in a dissolved or dispersed, that is to say suspendedor emulsified form. The active substance concentration in these liquidsis typically in the range of from 0.001 to 10 g/l. The use of the spraygun is in this regard not restricted to specific plant protection activesubstances and is suitable for the application of all active substanceswhich are usually employed in plant protection and are used in the formof liquid application forms, including low-viscosity or gel-likeapplication forms. These include in principle all plant protectionactive substances from the group of rodenticides, herbicides, herbicidesafeners, fungicides, insecticides, acaricides, nematicides,molluscicides, virucides, bactericides, algicides, growth regulators,pheromones, above all sexual pheromones (mating disruptors) andactivators and also fertilizers.

The present invention relates, furthermore, to the use of theabove-described spray gun for the expulsion of the following liquidproducts:

-   -   Aqueous active substance preparations of active substances, in        particular plant protection active substances, which are        obtainable by dilution of active substance concentrates with        water to the desired application concentration and which        comprise one or more of the abovementioned plant protection        active substances in dissolved or dispersed form.    -   Non-aqueous solutions or suspensions of active substances, in        particular plant protection active substances, which comprise        the active substance in a concentration suitable for        application.    -   Aqueous gel-like liquids which comprise one or more active        substances, in particular plant protection active substances,        especially from the group of insecticides, acaricides or        pheromones, and which, with suitable viscosity, are applied as        such or optionally after dilution with water to the desired        application concentration, and which comprise one or more of the        abovementioned plant protection active substances in dissolved        or dispersed form, and also water, at least one thickener or gel        former and optionally one or more attractants and/or feeding        stimulants.

The spray gun according to the invention can be used in a wide varietyof sectors of plant protection, in particular for the treatment ofplants, especially of their leaves (foliar application), but also forthe treatment of plant materials capable of propagation (seed). Thespray gun according to the invention is also suitable for the treatmentof inanimate materials, in particular of inanimate organic materials,such as wood, straw, paper, leather, textiles or plastic, or ofinanimate inorganic materials, such as glass or metal, which areinfected with harmful organisms or are intended to be protected frominfection with harmful organisms, such as fungi or insects, with aliquid active substance composition, which contain one or more suitableactive substances.

Moreover, such materials can be hung up as bait and be charged orrecharged with a suitable formulation by means of the spray gun.

The plant protection composition is in particular not atomized by thespray gun as in conventional application, but is applied to the targetarea in the form of a compact jet. In this case, application may takeplace at a single point (spot application) or may cover a strip arisingfrom forward movement. On account of the consistency of the plantprotection composition, the quantities applied remain adhering to thetarget area. The plant protection composition therefore has inparticular a gel consistency.

The above-described spray gun is used in particular for the expulsion ofplant protection compositions, the rheological properties of which areselected such that they are temperature independent or at least scarcelytemperature dependent. Preferably, the rheological properties of theplant protection composition change within a temperature range of from15° C. to 35° C. only such that the quantity expelled per unit time at agiven pressure at a particular nozzle or spray orifice fluctuates onlyin a range of +/−10%, in particular in a range of +/−5%.

Exemplary embodiments of the spray gun according to the invention areexplained in detail in the following text with reference to thedrawings, in which:

FIG. 1 schematically shows the structure of a first exemplary embodimentof the spray gun according to the invention and the coupling of thisspray gun to a fluid reservoir and to a compressed gas container,

FIG. 2 schematically shows the structure of a second exemplaryembodiment of the spray gun according to the invention and the couplingof this spray gun to a fluid reservoir and to a compressed gascontainer,

FIG. 3 schematically shows the structure of a third exemplary embodimentof the spray gun according to the invention and the coupling of thisspray gun to a fluid reservoir,

FIG. 4 schematically shows the structure of a fourth exemplaryembodiment of the spray gun according to the invention and the couplingof this spray gun to a fluid reservoir,

FIG. 5 schematically shows the structure of a fifth exemplary embodimentof the spray gun according to the invention and the coupling of thisspray gun to a fluid reservoir,

FIG. 6 schematically shows the structure of a sixth exemplary embodimentof the spray gun according to the invention and the coupling of thisspray gun to a fluid reservoir, and

FIG. 7 shows a diagram which illustrates the relationship of the fluidloss depending on the mixing ratio between the active substance andwater, i.e. of the viscosity of the fluid, and on the distance betweenthe spray nozzle and the fluid valve.

First of all, the first exemplary embodiment of the spray gun accordingto the invention is explained with reference to FIG. 1:

The spray gun comprises a cylinder 1, in which there is formed a fluidchamber 3. Formed at one end face of the cylinder 1 is a cylinderorifice 53 for filling the fluid chamber 3 with fluid. The cylinderorifice 53 is connected to a fluid reservoir 51 via a fluid line 50 anda valve 49. The valve 49 is an electrically activatable andelectromagnetically actuable valve which is coupled to a control device28. The control device 28 controls the opening and closing of the valve49. When the valve 49 is opened by means of the control device 28, fluidflows from the fluid reservoir 51 into the fluid chamber 3 via the line50. When the fluid chamber 3 is completely full, the valve 49 is closedagain by means of the control device 28.

At the end face of the cylinder 1, the latter has a further cylinderorifice 5, which is connected to a spray nozzle 22 via a line 20. Formedin the spray nozzle 22 is a spray orifice. The spray nozzle is designedsuch that a fluid jet 23 is created when a fluid, for which the spraygun is configured, is pressed under pressure through the spray nozzle22.

Arranged immediately upstream of the spray nozzle 22, that is to say atthat end of the line 20 which is adjacent to the spray nozzle 22, is anelectrically activatable fluid valve 48 for opening and closing thepassage from the fluid chamber 3 to the spray orifice of the spraynozzle 22. The distance of the spray orifice of the spray nozzle 22 fromthe fluid valve 48 is in this exemplary embodiment less than 5 cm,preferably less than 2 cm. In order to electrically activate the fluidvalve 48, the latter is data-coupled to the control device 28. By meansof a control signal which is generated by the control device 28, thefluid valve 48 can be opened for a precisely defined time interval andcan be closed again after the end of the time interval.

In order to exert a pressure on a fluid located in the fluid chamber 3,the spray gun comprises a pressure device. In the exemplary embodimentshown in FIG. 1, a piston 2 is mounted movably in the cylinder 1 forthis purpose. The cylinder 1 is subdivided in a fluid-tight manner bythe piston 2 into the fluid chamber 3 for the fluid to be expelled and apressure chamber 4. Provided in the pressure chamber 4 is a furthercylinder orifice 6, which is connected via a line 16 and a compressedgas valve 17 to a device for providing compressed air, for example acompressed air cylinder 18. The compressed gas valve 17 is also anelectrically activatable and electromagnetically actuable valve which isdata-coupled to the control device 28. The control device 28 canregulate the pressure in the pressure chamber 4 via the compressed gasvalve 17. Provided for this purpose in the pressure chamber 4 is apressure sensor 52, which detects the pressure in the pressure chamber 4and transmits a corresponding measured value to the control device 28.

Furthermore, an electronic, manually actuable trigger 31 is provided andis coupled to the control device 28. By actuating the trigger 31, theuser can initiate an expulsion operation.

The manner in which the above-described spray gun is calibrated isdescribed in the following text:

First of all, the fluid valve 48 is closed by the control device 28.Then, the valve 49 is opened by the control device 28 and a particularfluid of known viscosity is introduced into the fluid chamber 3 from thefluid reservoir 51. During this operation, the piston 2 is movedoptionally in the direction of an increase in the volume of the fluidchamber 3. Once the fluid chamber 3 has been filled with a particularquantity of fluid, the valve 49 is closed by the control device 28.Thereupon, the control device 28 generates a particular pressure in thepressure chamber 4. For this purpose, the control device 28 activatesthe compressed gas valve 17 and checks the pressure in the pressurechamber 4. Optionally, the compressed gas valve 17 can have an outletorifice via which compressed air can be let out of the pressure chamber4 in order to lower the pressure in the pressure chamber 4. This lettingout of compressed air via the outlet orifice in the compressed gas valve17 is also controlled by the control device 28. The pressure generatedin the pressure chamber 4 is transmitted to the fluid, which is locatedin the fluid chamber 3, via the movable piston 2. The pressure issufficiently large for the operation of expelling the fluid via thespray nozzle 22.

Subsequently, the fluid valve 48 is opened for a particular timeinterval by means of the control device 28. During this time interval,fluid is expelled from the fluid chamber 3 via the spray nozzle 22. Theexpelled fluid is collected and the expelled volume and/or the expelledweight are measured. Subsequently, the pressure during the expulsionoperation, the viscosity of the expelled fluid, the length of the timeinterval for which the fluid valve 48 was open, and the volume and/orthe weight of the expelled fluid are stored in a memory 54 in thecontrol device 28. Optionally, this operation is repeated at differentpressures and time intervals until the desired parameters for theexpulsion operation have been set for the fluid having the definedviscosity. These parameters, that is to say the viscosity of the fluid,the pressure during the expulsion operation and the length of the timeinterval for the expulsion operation are stored as setpoint values inthe memory 54 in the control device 28. Moreover, the calibration can beexecuted before each series of expulsions. In this case, storing in amemory is not necessary. Optionally, the temperature of the fluid duringthe expulsion operation can additionally be sensed and stored. Thecalibration can be carried out for fluids of different viscosities.

Thus, a pressure and a length of a time interval for the expulsion of afluid, for example a plant protection composition, having a particularviscosity are set in advance.

In the following text, an exemplary embodiment of the method accordingto the invention is described, as is carried out by means of the spraygun described with reference to FIG. 1 following calibration:

As in the calibration operation, the fluid chamber 3 is filled with aparticular fluid volume from the fluid reservoir 51. The volume in thefluid chamber 3 is in this case sufficient for a series of expulsionoperations. Subsequently, the valve 49 is closed by means of the controldevice 28. Then, the control device 28 uses the pressure sensor 52 andthe compressed gas valve 17 to regulate the pressure of the compressedair in the pressure chamber 4 such that it corresponds to the valuewhich was determined during the previously carried out calibrationoperation.

The user now manually actuates the trigger 31. The electronic trigger 31thereupon transmits a corresponding control signal to the control device28. The control device 28 now checks whether the pressure in thepressure chamber 4 corresponds, optionally with a certain tolerance, tothe pressure which is stored in the memory 54 and was set during thecalibration. If the measured actual pressure corresponds to the storedsetpoint pressure, optionally with a tolerance range being taken intoconsideration, the control device 28 opens the fluid valve 48 preciselyfor a time interval, the length of which is stored in the memory 54 inthe control device 28 and was set during the calibration. To this end,the control device 28 transmits a corresponding control signal to thefluid valve 48. For example, a voltage is applied to the fluid valve 48for the length of the time interval. After the end of the time interval,the fluid valve 48 is closed again by means of the control device 28.For example, the applied voltage is set back to zero so that the fluidvalve 48 closes again.

During the time interval for which the fluid valve 48 is open, the fluidlocated in the fluid chamber 3 is expelled as a fluid jet 23 via thespray orifice in the spray nozzle 22. The length of the time interval isfor example in a range of from 0.5 second to 6 seconds, in particular ina range of from 1 second to 3 seconds. During this period of time, thecontrol device 28 regulates the pressure in the pressure chamber 4 suchthat it is constant, that is to say that a constant pressure is exertedvia the piston 2 on the fluid in the fluid chamber 3.

In the method according to the invention, a gel-like plant protectioncomposition is expelled. The plant protection composition isviscoelastic and has a dynamic viscosity in a range of from 30 to 1000mPa·s, frequently in a range of from 30 to 800 mPa·s and in particularin a range of from 50 to 500 mPa·s (determined by Brookfield'srotational viscometry to DIN 53019 (ISO 3219) at 25° C. and with a sheargradient of 100 s⁻¹).

The rheological properties of the formulation of the plant protectioncomposition are selected such that they are temperature independent orat least scarcely temperature dependent. The rheological properties ofthe formulation of the plant protection composition change within atemperature range of from 15° C. to 35° C. for example only such thatthe quantity expelled per unit time at a given pressure at a particularspray nozzle 22 fluctuates only in a range of +/−10%, in particular in arange of +/−5%.

A second exemplary embodiment of the spray gun according to theinvention is explained in the following text with reference to FIG. 2:

In the second exemplary embodiment, parts which have the same functionas in the first exemplary embodiment are designated by the samereference signs. The function of these parts is also the same as in thefirst exemplary embodiment, and therefore the description of these partsis not repeated in detail.

The spray gun comprises a piston metering or piston pumping device,which has a cylinder 1 and a piston 2 which is mounted movably in thecylinder 1. The cylinder 1 is subdivided in a fluid-tight manner by thepiston 2 into a fluid chamber 3 for the fluid to be expelled and apressure chamber 4. Provided in the fluid chamber 3 is a first cylinderorifice 5, through which the fluid chamber 3 can be filled with fluidand through which, moreover, fluid is pressed out of the fluid chamber 3during the expulsion operation. In the pressure chamber 4, a secondcylinder orifice 6 is formed in the cylinder 1 and is connected to afirst connection 7 for a compressed gas line 8, as is explained later.

Furthermore, in the cylinder 1 there is provided an orifice, throughwhich the shank 9 of the piston 2 passes and in which this shank 9 ismounted in a gas-tight manner in a bearing 10. Mounting takes place inthis case in such a way that the piston 2 can be moved back and forth inthe longitudinal direction of the cylinder 1, so that the volume of thefluid chamber 3 and of the pressure chamber 4 is varied as a result ofthe movement of the piston 2. Furthermore, seals are provided in themounting, so that no compressed gas can escape from the pressure chamber4 through this orifice.

That part of the shank 9 of the piston 2 which passes through thefurther orifice in the cylinder 1 extends into a further cylinder 11.The rear end of the piston 2 is provided with a plate 12 which indicatesthe position of the piston 2 to the user. For this purpose, the cylinder11 is formed in an at least partially transparent manner. In addition,the plate 12 serves for coupling the piston 2 to a compression spring 13which is coupled at one end to the plate 12 and at the other end to aterminating wall 15 of the cylinder 11. The compression spring 13 exertson the piston 2 a force which acts in the direction of a reduction inthe volume of the fluid chamber 3.

Furthermore, provided at the rear end of the cylinder 11, near theterminating wall 15, is a regulating device which limits the movement ofthe piston 2 in the direction of an increase in the volume of the fluidchamber 3. The maximum volume of the fluid chamber 3 is thus set bymeans of the regulating device. In the present exemplary embodiment, theregulating device is in the form of a screw 14 which is received in aninternal thread of the terminating wall 15 of the cylinder 11. By thescrew 14 being rotated in this internal thread, the length of thatportion of the screw 14 which extends into the cylinder 11 can be set.If the piston 2 moves, as is explained later, in the direction of thescrew 14 during the filling of the fluid chamber 3 with fluid, thismovement of the piston 2 is limited by an abutment of the plate 12against the screw 14.

In order to press the piston 2 in the direction of the first cylinderorifice 5, that is to say to the left in FIG. 2, the gas pressure in thepressure chamber 4 is increased via the second cylinder orifice 6. Inthe present exemplary embodiment, compressed air is introduced into thepressure chamber 4 via the line 16. The line 16 is connected to acompressed gas valve 17, the function of which is explained later.

As in the first exemplary embodiment, a pressure sensor 52 is providedin the pressure chamber 4 and is coupled to the control device 28. Theair pressure in the pressure chamber 4 is increased until the forceexerted on the piston 2 by the compressed air and, optionally, thecompression spring 13 in the direction of the first cylinder orifice 5exceeds the force which is exerted on the piston 2 in the oppositedirection by the fluid located in the fluid chamber 3. It is pointed outthat this propulsive pressure for the piston 2 may also be exerted onlyby the compressed gas in the pressure chamber 4, only by the compressionspring 13 or both by the compressed gas in the pressure chamber 4 and bythe compression spring 13.

The first cylinder orifice 5 is connected via a line 20 and a fluidvalve 21 to a spray nozzle 22 which provides a spray orifice. The fluidexpelled by the spray gun flows out through the spray orifice in a fluidjet 23. The pressure exerted on the fluid may for example be so highthat the emerging fluid jet can be shot onto a target area over adistance of two to three meters. The pressure exerted on the fluid mayfor example be in a range of from 2 bar to 6 bar.

As in the first exemplary embodiment, an electrically activatable fluidvalve 48, which is coupled to the control device 28, is arrangeddirectly at the spray nozzle 22. It can be opened and closed by acontrol signal from the control device 28.

The fluid to be expelled is conveyed into the fluid chamber 3 asfollows:

Provided for a fluid stock 26 is a fluid reservoir 24 which is connectedto a connection 32 of the spray gun via a line 25. This connection 32 iscoupled to a connection of the fluid valve 21 which is in the form of a3/2-way valve. The further connections of the 3/2-way valve areconnected to the first cylinder orifice 5 and to the spray nozzle 22. Inthe first position of the fluid valve 21, a fluid passage from the firstcylinder orifice 5 to the spray nozzle 22 is provided. However, in asecond position of the fluid valve 21 a fluid passage from the fluidreservoir 24 via a line 25 through the fluid valve 21 to the line 20 andfinally to the first cylinder orifice 5 is provided. Thus, in the secondposition of the fluid valve 21, a fluid 26 which is located in the fluidreservoir 24 can be conveyed into the fluid chamber 3. The fluid 26 canin this case enter the fluid chamber 3 as a result of gravity or bymeans of a pump. However, in the present exemplary embodiment the fluidreservoir 24 is acted on with compressed air, which presses the fluid 26into the fluid chamber 3. For this purpose, the fluid reservoir 24 isconnected via a line 8 to a device 18 for the provision of compressedair. The device 18 may for example be a compressed air tank, acompressor and a hand pump. Furthermore, a shut-off valve 19 mayoptionally be arranged in the line 8.

Furthermore, the fluid reservoir 24 is connected via a line 27 to thefirst connection 7 of the compressed gas valve 17, which is also in theform of a 3/2-way valve. In the first position of this compressed gasvalve 17, a compressed gas passage from the compressed air line 8 viathe first connection 7 through the compressed gas valve 17 and the line16 to the second cylinder orifice 6 into the pressure chamber 4 isprovided. By contrast, in the second position of the compressed gasvalve 17, this passage is closed and a compressed gas passage from theline 16 via a third connection 33 into the open is provided. Thus, inthe second position, the pressure in the pressure chamber 4 can bereduced.

The fluid valve 21 and the compressed gas valve 17 may beelectromagnetically actuable. They are connected to the control device28, which can actuate them. In this case, as described above, the valves17 and 21 can be changed over from the first position into the secondposition, and vice versa. For this purpose, the control device 28 maycomprise for example a relay or a microprocessor.

Furthermore, the control device 28 is connected to a sensor 29. Thesensor 29 may for example be in the form of a reed switch or comprise areed contact. This contact is closed when the field strength of amagnetic field at the sensor 29 exceeds a limit value. The controldevice 28 detects whether the reed contact of the sensor 29 is closed oropen.

The position of the piston 2 in the cylinder 1 can be detected by meansof the sensor 29. In the spray gun according to the invention, aparticular position of the piston 2 within the cylinder 1, in whichposition the expulsion operations are intended to be ended, is defined.The sensor 29 changes its state precisely in this defined position ofthe piston 2. This is detected by the control device 28. In order tobring about this change of state of the sensor 29, a permanent magnet 30is integrated in the piston 2. This permanent magnet 30 generates amagnetic field, the field strength of which at the location of thesensor 29 depends on the position of the piston 2. If the piston 2 is inthe defined position explained above, the magnetic field generated bythe permanent magnet 30 causes a change of state in the sensor 29.

The filling of the fluid chamber 3 and the fluid expulsion in the secondexemplary embodiment of the spray nozzle are explained in detail in thefollowing text:

When the fluid chamber 3 is being filled with fluid, both the fluidvalve 21 and the compressed gas valve 17 are in the second position. Inthis case, the fluid 26 in the fluid reservoir 24 is conveyed throughthe line 25 and through the fluid valve 21 via the line 20 into thefluid chamber 3 of the cylinder 1. The pressure exerted by thecompressed air is in this case so high that the piston 2 is moved to theright in FIG. 2, specifically counter to the force which is exerted bythe compression spring 13. During the movement of the piston 2, the airin the pressure chamber 4 escapes outward through the line 16, thecompressed gas valve 17 and the third connection 33. The fluid chamber 3can be filled with fluid, with the volume of the fluid chamber 3increasing as a result of the movement of the piston 2, until the plate12 of the piston 2 butts against the screw 14. When the piston 2 is atthis stop, the maximum set volume of the fluid chamber 3 is reached andthe fluid chamber 3 is completely filled with fluid.

If the trigger 31 is now actuated by a user, a corresponding signal istransmitted to the control device 28. The control device 28 thereuponswitches the compressed gas valve 17 and the fluid valve 21 into thefirst position. In this position, the fluid supply from the fluidreservoir 24 is shut off, but the fluid passage from the fluid chamber 3to the fluid valve 48 is open. Moreover, at the same time or preferablyshortly beforehand, the compressed gas passage from the compressed airline 8 into the pressure chamber 4 is opened, so that compressed air isintroduced into the pressure chamber 4.

As in the first exemplary embodiment, the control device 28 nowregulates the pressure in the pressure chamber 4 such that itcorresponds to the value which was determined during the calibration andis stored in the memory 54 in the control device 28. If the actualpressure measured corresponds to the stored setpoint pressure, thecontrol device 28 uses a control signal to open the fluid valve 48 for atime interval, the length of which is stored in the memory 54 in thecontrol device 28 and which was determined previously during thecalibration. After the end of the time interval, the fluid valve 48 isclosed again by means of the control device 28. For the length of thetime interval, a fluid jet 23 was expelled during the expulsionoperation.

In this way, a plurality of expulsion operations can now be carried out.In this case, the piston 2 moves in the direction of a reduction in thevolume of the fluid chamber 3.

When the piston 2 now reaches the defined position explained above, thepermanent magnet 30 generates at the sensor 29 a magnetic field having afield strength which leads to a change of state of the sensor 29. Such achange of state is detected by the control device 28, whereupon thecontrol device 28, after the conclusion of the expulsion operation andafter the closure of the fluid valve 48, switches the fluid valve 21 andthe compressed gas valve 17 in each case back into the second positionagain. The changeover of the two valves 17 and 21 may take placesimultaneously. Furthermore, it is possible for the fluid valve 21 to bechanged over first, and only shortly thereafter the compressed gas valve17.

Once the two valves 17 and 21 have been moved into the second position,the fluid chamber 3 is automatically filled with fluid again for thenext expulsion operations, as explained above.

The third exemplary embodiment of the spray gun according to theinvention is explained in the following text with reference to FIG. 3:

In the third exemplary embodiment, parts which have the same function asin the first and second exemplary embodiments are designated by the samereference signs. The function of these parts is also the same as in thefirst and/or second exemplary embodiment, and therefore the descriptionof these parts is not repeated in detail.

The third exemplary embodiment of the spray gun differs from the secondexemplary embodiment in particular in that the pressure chamber 4 of thesecond exemplary embodiment has been converted into a second fluidchamber 34. A first fluid chamber 3 and a second fluid chamber 34, whichare separated from one another by the movable piston 2, are thus formedin the cylinder 1. Furthermore, the compression spring 13 of the secondexemplary embodiment has been omitted.

As in the second exemplary embodiment, the first fluid chamber 3 isconnected via the first cylinder orifice 5 and a line 20 to a fluidvalve 21 which is designated as a first fluid valve 21 in this thirdexemplary embodiment. The first fluid valve 21, too, is in the form of a3/2-way valve. As in the second exemplary embodiment, a connection ofthe first fluid valve 21 is connected to the spray nozzle 22. However,in the third exemplary embodiment a third fluid valve 35 is arrangedbetween the connection of the first fluid valve 21 and the spray nozzle22, as is explained later.

As in the second exemplary embodiment, the connection 32 of the firstfluid valve 21 is connected to a fluid reservoir 24 in which fluid 26 islocated. As in the second exemplary embodiment, the fluid reservoir 24can be acted on with compressed air by means of the compressed air line8, the shut-off valve 19 and the device 18 for the provision ofcompressed air. However, in all the exemplary embodiments, the fluid mayalso be put under pressure in another way, in order to move the piston2, as explained later. For example, a pump may be used. In this case,there may also be provided a bypass, via which the fluid passes backinto the reservoir when the cylinder 1 is not filled, because at leastone fluid valve or a plurality of fluid valves is or are closed.

Unlike in the second exemplary embodiment, in the third exemplaryembodiment the second cylinder orifice 6, which in this case is arrangedat the second fluid chamber 34, is connected to a second fluid valve 36via the line 16. This second fluid valve, too, is designed as a 3/2-wayvalve. The connection 37 of the second fluid valve 36 is connected tothe fluid reservoir 24 via a line 38. The other connection 41 of thesecond fluid valve 36 is connected to the spray nozzle 22 via the thirdfluid valve 35.

The third fluid valve 35 is in the form of a 3/3-way valve with ashut-off middle position. A passage from the line 39 to the spray nozzle22 or from the line 40 to the spray nozzle 22 can thus be produced.Furthermore, both passages may be shut off.

As in the second exemplary embodiment, a sensor 29 in the form of a reedswitch is arranged in the first fluid chamber 3 and is designated as afirst sensor 29 in the third exemplary embodiment. If the permanentmagnet 30 of the piston 2 is in the defined position explained withregard to the second exemplary embodiment, this permanent magnet 30generates a magnetic field, the field strength of which at the locationof the first sensor 29 causes the reed contact to be closed. This isdetected by the control device 29.

However, in the third exemplary embodiment, in contrast to the secondexemplary embodiment, a corresponding second sensor 39 is located in thesecond fluid chamber 34. The second sensor 39, too, comprises a reedcontact. In the spray gun of the third exemplary embodiment there isdefined a further position of the piston 2, in which the expulsionoperation is intended to be ended, specifically, in this case, theoperation of expelling the fluid out of the second fluid chamber 34. Thesecond sensor 39 is designed such that the reed contact is closed whenthe permanent magnet 30 of the piston 2 generates, in a correspondinglydefined position, a magnetic field, the field strength of which at thelocation of the second sensor 39 exceeds the limit value for switchingthe reed contact. This change of state of the second sensor 39 is alsodetected by the control device 28.

Furthermore, the two sensors 29, 39 may be adjustable in thelongitudinal direction of the cylinder 1. In this case, the fluid volumeto be discharged can be adapted by the position of the sensors 29, 39being changed.

Furthermore, the spray gun of the third exemplary embodiment, too, has afluid valve 48 directly at the spray nozzle 22, said fluid valve 48being electrically activatable by the control device 28. Furthermore, ineach of the two fluid chambers 3 and 34 there is arranged a pressuresensor (not shown), which measures the pressure in each fluid chamber 3,34 and transmits it to the control device 28.

The spraying operation with the spray gun according to the thirdexemplary embodiment is explained in the following text:

Before the actual spraying operation, the cylinder 1 of the spray gun isfilled with fluid 26 from the fluid reservoir 24. In this initial state,the control device 28 first activates the third fluid valve 35 such thatthe passages in the direction of the spray nozzle 22 are shut off, thatis to say the third fluid valve 35 is in the middle position.Furthermore, the fluid valve 48 is closed. Thereupon, the first fluidvalve 21 is activated by the control device 28 such that a fluid passagefrom the fluid reservoir 24 into the first fluid chamber 3 is created.If the shut-off valve 19 is now opened, the fluid reservoir 24 is actedon with compressed air, so that fluid 26 flows via the line 25 throughthe first fluid valve 21 into the first fluid chamber 3. Alternatively,in this case, too, the fluid may be put under pressure, for example bymeans of a pump. Thus, in the illustration according to FIG. 3, thepiston 2 is moved to the right until it butts against a stop (notillustrated). If, in this case, air is still located in the second fluidchamber 34, an outlet valve for displacing this air may be provided. Iffluid 26 is already located in the second fluid chamber 34, the secondfluid valve 36 is activated by the control device 28 such that the fluidpassage between the line 38 and the line 16 is opened, so that the fluidin the second fluid chamber 34 can flow back into the reservoir 24.

If the trigger 31 is now actuated by a user, the control device 28switches the first fluid valve 21 for a fluid passage from the line 20into the line 39. The fluid passage from the line 20 into the line 25 isshut off. By contrast, the second fluid valve 36 is switched such thatthe fluid passage from the line 38 into the line 16 is opened, but thefluid passage from the line 16 into the line 40 is shut off.Furthermore, the control device 28 activates the third fluid valve 35such that the fluid passage from the line 39 to the fluid valve 48 isopened, but the fluid passage from the line 40 to the fluid valve 48 isshut off. This switching of the three fluid valves 21, 36 and 35 has theeffect that, by the fluid reservoir 24 being acted on with compressedair, fluid 26 flows via the line 38 through the second fluid valve 36into the second fluid chamber 34. The fluid in the second fluid chamber34 exerts a force on the piston 2 so that the latter is pressed in thedirection of a reduction in the volume of the first fluid chamber 3, tothe left in the illustration according to FIG. 3. The fluid located inthe first fluid chamber 3 is thus pressed through the first cylinderorifice 5 via the line 20, through the first fluid valve 21 via the line39 and through the third fluid valve 35 to the fluid valve 48.

If, as in the first two exemplary embodiments, the pressure exerted onthe fluid now corresponds to the setpoint value stored in the controldevice 28, the control device 28 opens the fluid valve 48 for thepreviously set time interval, the length of which is stored in thememory 54 in the control device 28, and the fluid is expelled as a fluidjet 23. Such an expulsion operation can be repeated until the magneticfield generated by the permanent magnet 30, at the location of the firstsensor 29, exceeds a field strength which brings about a change of stateof the first sensor 29, said change of state being detected by thecontrol device 28. As soon as this change of state has been detected,the control device 28 changes over the three fluid valves 21, 36 and 35,after the conclusion of the last expulsion operation, as follows: thefirst fluid valve 21 is switched such that the passage from the line 20to the line 39 is shut off, but the passage from the line 25 to the line20 is opened. The second fluid valve 36 is changed over such that thefluid passage from the line 38 into the line 16 is shut off, but thefluid passage from the line 16 into the line 40 is opened. Furthermore,the third fluid valve 35 is changed over such that it is moved into thecompletely shutting-off middle position or such that it is moveddirectly into a position in which the fluid passage from the line 40 tothe spray nozzle 22 is opened, but the fluid passage from the line 39 tothe spray nozzle 22 is shut off. When the defined position of the piston2 has been detected, at least the first fluid valve 21 or the thirdfluid valve 35 for the passage from the first fluid chamber 3 to thespray nozzle 22 is shut off.

This changing over of the three fluid valves 21, 36, 35 has the effectthat the fluid 26 now flows the other way round under pressure via theline 25, through the first fluid valve 21 into the first fluid chamber3. Here, the fluid exerts a force upon the piston 2 so that the latteris moved in the direction of a reduction in the volume of the secondfluid chamber 34, to the right in the illustration according to FIG. 3.The first fluid chamber 3 is now filled. However, as a result of thisfilling, the fluid located in the second fluid chamber 34 is pressed viathe line 16, through the second fluid valve 36, via the line 40, throughthe third fluid valve 35, to the fluid valve 48.

A series of expulsion operations of the fluid located in the fluidchamber 34 can now again take place. These expulsion operations lastuntil the magnetic field generated by the permanent magnet 30 at thelocation of the second sensor 39 reaches a field strength which causes achange of state of the second sensor 39. As soon as such a change ofstate has been detected by the control device 28, after the conclusionof the last expulsion operation, the fluid valves 21, 36 and 35 areswitched back again, as explained above, so that subsequently the secondfluid chamber 34 is filled.

The fluid is expelled from the spray gun of the third exemplaryembodiment, as in the spray gun of the first or second exemplaryembodiment, as a fluid jet 23 which has a constant expulsion velocity upto the end of the expulsion operation, so that the fluid jet 23 reachesits target completely. Moreover, the fluid valve 48 prevents fluid fromdripping.

The fourth exemplary embodiment of the spray gun according to theinvention is explained in the following text with reference to FIG. 4:

In the fourth exemplary embodiment, parts which have the same functionas in the preceding exemplary embodiments are designated by the samereference signs. The function of these parts is also the same as in thepreceding exemplary embodiments, and therefore the description of theseparts is not repeated in detail.

The basic functioning of the spray gun of the fourth exemplaryembodiment corresponds to the spray gun of the third exemplaryembodiment. However, in this case a single cylinder 1 comprising twofluid chambers 3 and 34 which are separated by the piston 2 is notprovided, but rather two cylinders 1-1 and 1-2 are provided. However,the functional principle corresponds substantially to the functionalprinciple of the spray gun of the third exemplary embodiment.

A first fluid chamber 3-1 having a first cylinder orifice 5-1 is formedin the first cylinder 1-1. Furthermore, a first pressure chamber 4-1 isformed in the first cylinder 1-1. A movable first piston 2-1 is arrangedbetween the first fluid chamber 3-1 and the first pressure chamber 4-1.

Correspondingly, a second fluid chamber 3-2 with a second cylinderorifice 5-2 is formed in the second cylinder 1-2. A second pressurechamber 4-2 is formed in the second cylinder 1-2, too, a movable secondpiston 2-2 being arranged between the second fluid chamber 3-2 and thesecond pressure chamber 4-2. The first pressure chamber 4-1 and thesecond pressure chamber 4-2 communicate with one another via a line 42.A non-compressible working fluid, such as oil, for example, is locatedin the first and the second pressure chamber 4-1, 4-2 and the line 42.Furthermore, the line 42 may be connected to a reservoir 43 for theworking fluid. The volume of the working fluid in the two pressurechambers 4-1, 4-2 and the line 42 can be varied via the reservoir 43.The maximum volume of the two fluid chambers 3-1, 3-2 and consequentlythe expelled fluid volume can be set in this way.

Alternatively or in addition, as in the spray gun of the third exemplaryembodiment, the two sensors 29-1, 29-2 may be adjustable in thelongitudinal direction of the cylinder 1-1, 1-2, so that the fluidvolume to be discharged can be adapted by the position of the sensors29-1, 29-2 being varied.

The working fluid transmits a force exerted by the first piston 2-1 tothe second piston 2-2, and vice versa. The unit formed from the firstpiston 2-1, the working fluid and the second piston 2-2 thus correspondsto the piston 2 of the spray gun of the third exemplary embodiment.

The spray gun of the fourth exemplary embodiment comprises two fluidvalves 44 and 45. The fluid valve 44 is also designated as first fluidvalve 44 in the following text. Since the fluid valve 45 correspondsfunctionally to the third fluid valve 35 of the third exemplaryembodiment, this fluid valve 45 is also designated as third fluid valve45 in the following text.

The first cylinder orifice 5-1 of the first fluid chamber 3-1 isconnected via a line 46 to a connection of the first fluid valve 44 andof the third fluid valve 45. Furthermore, the second cylinder orifice5-2 of the second fluid chamber 3-2 is connected via a line 47 toanother connection of the first fluid valve 44 and to another connectionof the third fluid valve 45. A further connection of the first fluidvalve 44 is coupled via a line 25 to the fluid reservoir 24 in which thefluid 26 is located. As in the first exemplary embodiments, the fluidreservoir 24 is coupled via a compressed air line 8 and an optionalshut-off valve 19 to a device 18 for the provision of compressed air.However, it would also be possible to put the fluid under pressuredirectly, for example by means of a pump. The first fluid valve 44 isactivated by the control device 28. In one state of the first fluidvalve 44, a passage from the line 25 to the line 46 is provided, thepassage from the line 25 to the line 47 being shut off. In the otherstate, a passage from the line 25 to the line 47 is provided, thepassage from the line 25 to the line 46 being shut off.

The spray gun of the fourth exemplary embodiment, too, has a fluid valve48 directly at the spray nozzle 22, said fluid valve 48 beingelectrically controlled by means of the control device 28. Furthermore,pressure sensors (not shown), which are coupled to the control device 28are provided at the pressure chambers 4-1 and 4-2.

The third fluid valve 45 is activated by the control device 28, with inone state a passage from the line 46 to the fluid valve 48 being opened,whereas the passage from the line 47 to the fluid valve 48 is shut off.In another state, the passage from the line 46 to the fluid valve 48 isshut off, whereas the passage from the line 47 to the fluid valve 48 isopened. Furthermore, as in the spray gun of the third exemplaryembodiment, there is provided a middle position, in which both passagesto the fluid valve 48 are shut off.

Similarly to the spray guns of the preceding exemplary embodiments, afirst sensor 29-1 is provided for the first cylinder 1-1 in the firstfluid chamber 3-1 and detects the position of the first piston 2-1 onaccount of a magnetic field generated by a first permanent magnet 30-1.Likewise, a second sensor 29-2 is provided in the second fluid chamber3-2 of the second piston 1-2 and detects the position of the secondpiston 2-2, in that, as explained with regard to the third exemplaryembodiment, a change of state of the second sensor 29-2 is detected bymeans of the field strength of a magnetic field generated by a secondpermanent magnet 30-2 which is arranged at the second piston 2-2. As inthe spray gun of the third exemplary embodiment, the signals of the twosensors 29-1 and 29-2 are transmitted to the control device 28, whichactivates the two fluid valves 44 and 45 depending on these signals.

A spraying operation which is carried out by the spray gun of the fourthexemplary embodiment is explained in the following text:

As in the preceding exemplary embodiments, fluid expulsion is initiatedin that a user actuates the trigger 31, which is connected to thecontrol device 28.

First of all, the control device 28 activates the first fluid valve 44such that a fluid passage from the line 25 to the line 46 is provided,so that the first fluid chamber 3-1 can be filled with fluid 26. Thethird fluid valve 45 is first of all located in the middle position inwhich the two passages are shut off. The first fluid chamber 3-1 isfilled with fluid, as a result of which the piston 2-1 is moved to theright in the illustration according to FIG. 4, so that the volume of thefirst fluid chamber 3-1 increases. At the same time, on account of thetransmission of force by the working fluid, the second piston 2-2 movesto the left in the illustration according to FIG. 4, in the direction ofa reduction in the volume of the second fluid chamber 3-2. If air isstill located in the second fluid chamber 3-2 when the spray gun is putinto operation, an outlet valve (not shown) may be provided for thisair. The first piston 2-1 is moved in the direction of an increase inthe volume of the first fluid chamber 3-1 until the first piston 2-1butts against a stop which may be provided by a cylinder wall or, as inthe spray gun of the second exemplary embodiment, by an adjusting screw.The control device 28 subsequently changes over the first fluid valve 44such that a fluid passage from the line 25 into the line 47 is provided.Furthermore, the third fluid valve 45 is switched such that a fluidpassage from the line 46 to the spray nozzle 22 is opened.

By the action of pressure on the fluid reservoir 24, the fluid 26 is nowpressed through the first fluid valve 44 and the line 47 into the secondfluid chamber 3-2. Alternatively, as in the spray gun of the thirdexemplary embodiment, the fluid may also be put under pressure, forexample, by means of a pump. As a result, the second piston 2-2 is movedin the direction of an increase in the volume of the second fluidchamber 3-2. At the same time, on account of the communication betweenthe two pressure chambers 4-1 and 4-2, the first piston 2-1 is moved inthe direction of a reduction in the volume of the first fluid chamber3-1, as a result of which fluid is pressed out of the first fluidchamber 3-1 via the line 46, through the third fluid valve 45 to thefluid valve 48.

Now, as in the second and the third exemplary embodiment, the fluidvalve 48 can be opened for the previously set time interval definedduring the calibration, in order to expel the fluid as a fluid jet 23.The expulsion operations can be repeated until the first piston 2-1 hasreached the defined position, this being sensed by the first sensor29-1, as explained above. Following the conclusion of the last expulsionoperation, the control device 28 then switches the third fluid valve 45in such a way that the fluid passage from the line 46 to the fluid valve48 is shut off. The third fluid valve 45 is in this case moved inparticular into the completely shutting-off middle position. Thereupon,the first fluid valve 44 is changed over, so that a fluid passage fromthe line 25 to the line 46 is opened. The third fluid valve 45 is nowmoved into a position in which a passage from the line 47 to the fluidvalve 48 is provided. By the action of pressure on the fluid reservoir24, fluid 26 is now pressed through the first fluid valve 44 and theline 46 into the first fluid chamber 3-1. As a result, the first piston2-1 is moved in the direction of an increase in the volume of the firstfluid chamber 3-1. At the same time, the second piston 2-2 is moved inthe direction of a reduction in the volume of the second fluid chamber3-2, as a result of which the fluid located in the second fluid chamber3-2 is pressed through the line 47 and through the third fluid valve 45to the fluid valve 48. Subsequently, a new series of expulsionoperations can begin.

In the above-described four exemplary embodiments, it is furthermorepossible not to use a memory 54. Instead, the pressure exerted on thefluid in the fluid chamber 3, said pressure having previously been set,can be adjusted or regulated mechanically by means of a pressure valve,by means of a pump, for example via the regulation of the rotationalspeed of the pump, or by means of other techniques which are known perse.

A fifth exemplary embodiment of the spray gun according to the inventionis explained in the following text with reference to FIG. 5:

In the fifth exemplary embodiment, parts which have the same function asin the preceding exemplary embodiments are designated by the samereference signs. The function of these parts is also the same as in thepreceding exemplary embodiments, and therefore the description of theseparts is not repeated in detail.

The fifth exemplary embodiment is similar to the first exemplaryembodiment. However, in this case the fluid chamber 3 is not formed by acylinder but by a line, which, as shown in FIG. 5, is immersed in thefluid located in the fluid reservoir 51. The fluid is located at thebottom of the fluid reservoir 51 and an air reservoir which is closedoff in a gas-tight manner is located above the surface of the fluid.This air reservoir is connected to a pressure chamber 4 via a pressureline 58. The pressure chamber 4 is connected in turn, as in the firstexemplary embodiment, to a compressed air cylinder 18 via a line 16 anda compressed gas valve 17. The compressed gas valve 17 is controlled bythe control device 28 such that a constant previously set pressure isexerted on the fluid located in the fluid reservoir 51. This ensuresthat a pressurized fluid is always located in the fluid chamber 3 whichis in the form of a line.

As in the first exemplary embodiment, the fluid valve 48, which isactivated via the control device 28, is provided directly upstream ofthe spray nozzle 22. Provided in this case in the control device 28 is atimer, which determines the opening time of the fluid valve 48 duringthe expulsion of the fluid jet 23. As in the first exemplary embodiment,following the actuation of the trigger 31 by means of the control device28 the fluid valve 28 is opened for a previously set time interval and adefined volume or a defined weight of the fluid is expelled through thespray nozzle 22.

A sixth exemplary embodiment of the spray gun according to the inventionis explained in the following text with reference to FIG. 6:

In the sixth exemplary embodiment, parts which have the same function asin the preceding exemplary embodiments are designated by the samereference signs. The function of these parts is also the same as in thepreceding exemplary embodiments, and therefore the description of theseparts is not repeated in detail.

The structure of the sixth exemplary embodiment of the spray gun issimilar to the structure of the fifth exemplary embodiment of the spraygun. However, in this case a fluid pump 56 is arranged between the fluidchamber 3 in the form of a line and the fluid reservoir 51. A device forthe provision of compressed air is not required in this case.

That end of the fluid chamber 3 which is remote from the fluid valve 48is adjoined by the fluid pump 56, which is connected to the fluidreservoir 51 via the line 57. By means of the fluid pump 56, the fluidlocated in the fluid reservoir 51 is pumped out and pumped into thefluid chamber 3. Furthermore, there may be provided a bypass, via whichthe fluid can pass back into the fluid reservoir 51 if the pressureexerted on the fluid is too high. The fluid pump 56 is electricallycoupled to the control device 28 so that it can be activated by thecontrol device 28. Activation takes place such that a constant pressureis always exerted on the fluid located in the fluid chamber 3. For thispurpose, for example the rotational speed of the fluid pump can beregulated.

The expulsion operation then takes place in the same manner as in thefifth exemplary embodiment.

The spray guns of the second to sixth exemplary embodiments and themethods implemented by these spray guns are carried out in particularwith the plant protection compositions which were mentioned initiallyand with reference to the first exemplary embodiment.

In the above-described exemplary embodiments, the fluid valve 48 isarranged directly at the spray orifice 22. In a further, seventhexemplary embodiment, experiments were carried out to study what effectthe distance of the fluid valve 48 from the spray orifice 22 has on thedripping behavior at the nozzle when fluids having different viscositiesare expelled.

The structure of the seventh exemplary embodiment corresponds to thestructure of the first exemplary embodiment, apart from the distance ofthe fluid valve 48 from the spray orifice 22.

The fluid valve 48 was connected to the spray nozzle 22 via a flexibletube. The outside diameter of the flexible tube was 8 mm and the insidediameter was 6 mm. A Lechler 544.320 full-jet nozzle was used as thenozzle.

The spray nozzle 22, in which the spray orifice is formed, waspositioned 10 cm over an application area, which takes up a path lengthof 120 cm. In addition, the spray nozzle 22 was oriented such that theapplication jet likewise projects 10 cm beyond the application area atthe end of the path. In order to measure the loss of fluid during theexpulsion operation on the application area, previously tared paper waslaid out. The test was then carried out as follows: after a fluidreservoir had been filled, the system was conditioned with the substanceto be tested, i.e. a fluid having a particular viscosity was filled intothe fluid reservoir. Next, in order to avoid errors, the spray nozzle 22was dabbed dry directly prior to the first application. Each part of thetest consists of three applications, which were carried out at aspraying pressure of 3 bar. Each application lasted 1.5 seconds. Inorder to allow for possible dripping, 8.5 seconds were waited betweeneach discharge. At the end, the residual fluid from the spray nozzle 22was absorbed using the paper and weighed.

The test results are given in the following table:

Starting material Amount BAS from 3 310 Flexible tube applicationsObservations 63 I Water Viscosity Type Length [g] Application routeNozzle mouth 1 3 123.8 mPa · s Festo 8  0 cm 0.03 localized very Nodripping at small droplets on the nozzle the path 1 2 215.2 mPa · sFesto 8  0 cm 0.00 localized very No dripping at small droplets on thenozzle the path 1 1 579.0 mPa · s Festo 8  0 cm 0.01 localized very Nodripping at small droplets on the nozzle the path 1 3 123.8 mPa · sFesto 8  50 cm 0.17 Some drops Drips a little discernible 1 2 215.2 mPa· s Festo 8  50 cm 0.23 Some drops Drips a little discernible 1 1 579.0mPa · s Festo 8  50 cm 0.45 Some drops Drips a little discernible 1 3123.8 mPa · s Festo 8 100 cm 0.34 Increased Drips at the number of dropsnozzle seen on the path 1 2 215.2 mPa · s Festo 8 100 cm 0.41 IncreasedDrips at the number of drops nozzle seen on the path 1 1 579.0 mPa · sFesto 8 100 cm 0.60 Increased Drips at the number of drops nozzle seenon the path

FIG. 7 illustrates the relationship of the fluid loss depending on themixing ratio between the active substance and water, i.e. the viscosityof the fluid, and the distance between the spray nozzle 22 and the fluidvalve 28.

It has been found in tests that the application time has no effect onthe fluid loss, since, as soon as the spray jet has been built up, nodrops deviate from the target. However, when the spray jet is beingbuilt up and particularly when it is being broken down, drops could beregistered on the application path. In addition, there is dripping atthe nozzle opening. The results of the tests show greater loss with anincreasing “dead volume” between the valve 48 and the spray nozzle 22,i.e. with a greater distance between the valve 48 and the spray nozzle22. In particular at a distance of more than 50 cm, an undesired fluidloss arises. In this case, the loss is greater on the application route,the greater the viscosity of the fluid, i.e. the spray liquor, is. Theconsistency of the formulation thus also has a great influence on thefluid loss. A possible explanation for this is that the more viscousfluid absorbs more energy, which has to be released again after thefluid valve 48 is closed. This results in dripping. A further indicationtherefor was a required steeper incidence angle of the spray nozzle 22for more viscous fluids. This steeper incidence angle was required inorder to reach the target.

In preliminary tests, it was moreover found that tapering of theflexible tube between the spray nozzle 22 and the fluid valve 48 resultsin smaller losses. An increase in the pressure results in an increasedfluid loss on the path from the spray nozzle 22 to the target. However,fluid losses can be largely ruled out when a “dead volume” from thefluid valve 48 to the spray nozzle 22 is avoided, i.e. when the spraynozzle 22 is arranged directly at the fluid valve 48.

LIST OF REFERENCE SIGNS

-   1 Cylinder-   1-1 First cylinder-   1-2 Second cylinder-   2 Piston-   3 Fluid chamber; first fluid chamber-   3-1 First fluid chamber-   3-2 Second fluid chamber-   4 Pressure chamber-   4-1 First pressure chamber-   4-2 Second pressure chamber-   5 Cylinder orifice, first cylinder orifice-   5-1 First cylinder orifice-   5-2 Second cylinder orifice-   6 Cylinder orifice, second cylinder orifice-   7 First connection-   8 Compressed air line-   9 Shank of piston 2-   10 Bearing-   11 Cylinder-   12 Plate-   13 Compression spring-   14 Screw-   15 Terminating wall-   16 Line-   17 Compressed gas valve-   18 Device for the provision of compressed air, compressed air    cylinder-   19 Shut-off valve-   20 Line-   21 Fluid valve; first fluid valve-   22 Spray nozzle-   23 Fluid jet-   24 Fluid reservoir-   25 Line-   26 Fluid-   27 Line-   28 Control device-   29 Sensor; first sensor-   30 Permanent magnet-   31 Trigger-   32 Second connection-   33 Third connection-   34 Second fluid chamber-   35 Third fluid valve-   36 Second fluid valve-   37 Connection-   38 Line-   39 Line-   40 Line-   41 Connection-   42 Line-   43 Reservoir-   44 Fluid valve; first fluid valve-   45 Fluid valve; third fluid valve-   46 Line-   47 Line-   48 Fluid valve-   49 Fluid valve-   50 Fluid line-   51 Fluid reservoir-   52 Pressure sensor-   53 Cylinder orifice-   54 Memory-   55 Timer-   56 Fluid pump-   57 Line-   58 Compressed gas line

1-18. (canceled)
 19. A method for the expulsion of a plant protectioncomposition by means of a fluid chamber (3) which communicates with aspray orifice (22) via an electrically activatable fluid valve (48), themethod comprising setting a pressure and a length of a time interval forthe expulsion of the plant protection composition, filling the plantprotection composition into the fluid chamber (3), exerting thepreviously set pressure on the plant protection composition located inthe fluid chamber (3), and opening the fluid valve (48) for thepreviously set time interval by means of an electric control signal andclosing the fluid valve (48) after the end of the time interval so thata defined volume or a defined weight of the plant protection compositionis expelled through the spray orifice (22).
 20. The method according toclaim 19, wherein the pressure which is exerted on the plant protectioncomposition located in the fluid chamber (3) is kept constant during thetime interval in which the fluid valve (48) is open.
 21. The methodaccording to claim 19, wherein the pressure exerted on the plantprotection composition located in the fluid chamber (3) is generated bymeans of a pressurized gas or a pump.
 22. The method according to claim19, wherein the distance between the fluid valve (48) and the sprayorifice (22) is less than 50 cm.
 23. The method according to claim 19,wherein the fluid valve (48) is arranged directly at the spray orifice(22).
 24. The method according to claim 19, wherein the plant protectioncomposition is a gel-like fluid which has at 25° C. a dynamic viscositywhich is determined by Brookfield's rotational viscometry with a sheargradient of 100 s⁻¹ and is in the range of from 30 to 1000 mPa·s. 25.The method according to claim 19, wherein the rheological properties ofthe plant protection composition change within a temperature range offrom 15° C. to 35° C. only such that the quantity expelled per unit timeat a given pressure at a particular spray orifice (22) fluctuates onlyin a range of +/−10%.
 26. The method according to claim 19, wherein thelength of the time interval is set by a previously carried outcalibration in which the dependence of the expelled volume or weight ofa plant protection composition of a particular viscosity on the exertedpressure and the length of the time interval is determined.
 27. A spraygun for the expulsion of a fluid having a fluid chamber (3), a sprayorifice (22) which communicates with the fluid chamber (3), and apressure device (1, 2, 4, 16, 17, 18, 56) which is coupled to the fluidchamber (3) and by means of which a pressure can be exerted on the fluidlocated in the fluid chamber (3), wherein an electrically activatablefluid valve (48) for opening and closing the passage from the fluidchamber (3) to the spray orifice (22) is arranged at the spray orifice(22) and the fluid valve (48) is data-coupled to an electric controldevice (28) by way of which an electric control signal for opening thefluid valve (48) for a particular previously set time interval and forclosing the fluid valve (48) after the end of the time interval can begenerated so that a defined volume or a defined weight of the fluid isexpelled via the spray orifice (22).
 28. The spray gun according toclaim 27, wherein said fluid is a plant protection composition.
 29. Thespray gun according to claim 27, wherein the control device (28)comprises a memory (54) for storing a previously set pressure and thepreviously set length of the time interval.
 30. The spray gun accordingto claim 27, wherein the pressure device (1, 2, 4, 16, 17, 18, 56)comprises a fluid pump (56), by means of which the pressure can beexerted on the fluid located in the fluid chamber (3).
 31. The spray gunaccording to claim 27, wherein the pressure device (1, 2, 4, 16, 17, 18,56) comprises a compressed gas line (16) which is coupled to the fluidchamber (3) for exerting the pressure on the fluid located in the fluidchamber (3).
 32. The spray gun according to claim 27, wherein the fluidchamber (3) and the spray orifice (22) are connected together via aconnecting line (20), and wherein the fluid valve (48) is arrangedadjacent to the spray orifice (22) in the connecting line (20).
 33. Thespray gun according to claim 27, wherein the distance between the fluidvalve (48) and the spray orifice (22) is less than 50 cm.
 34. The spraygun according to claim 27, wherein the fluid valve (48) is arrangeddirectly at the spray orifice (22).
 35. The spray gun according to claim27, wherein the spray gun is configured for a gel-like plant protectioncomposition and the spray orifice is surrounded by a spray nozzle (22)which generates a jet (23) when the gel-like plant protectioncomposition passes through.